ABSTRACT Support is requested for a Keystone Symposia conference entitled T Cell Dysfunction, Cancer and Infection, organized by Drs. Daniel C. Douek, W. Nicholas Haining and Jedd D. Wolchok. The conference will be held January 16-20, 2018 at Beaver Run Resort, Colorado. T cell exhaustion is an acquired state of T cell dysfunction, associated with reduced T cell function, sustained expression of inhibitory receptors and a transcriptional state that is distinct from memory and effector T cells. T cell exhaustion is now recognized as a defining feature not only of chronic infections such as HIV, malaria and tuberculosis, but also of cancer. As a result, the search for effective approaches to reverse T cell exhaustion is the focus of immense therapeutic development. However, the similarities and differences between T cell dysfunction arising in chronic infection and tumors are not fully understood. Moreover, opportunities to identify new therapeutic approaches to reverse dysfunction based on parallels between the two disease states remain to be explored. This meeting will focus on the comparative biology and clinical therapeutics of T cell dysfunction in chronic viral infection and cancer. Drawing on leaders in fundamental T cell biology, computational science and clinical investigation, it will focus on common features and distinctive aspects of T cell dysfunction in cancer and chronic infection. The meeting will have broad relevance for T cell biology, tumor immunity, infectious disease and therapeutic development.